Method and apparatus for transmitting and receiving control signal for merging carriers in transmission

ABSTRACT

Embodiments of the present invention are directed to a method and apparatus for transmitting and receiving a control signal (for example, PDCCH signal) in an asymmetric multicarrier environment. The method for transmitting a control signal for an asymmetric multicarrier in a wireless connection system according to one embodiment of the present invention comprises: determining the size of a carrier indicator field (CIF) indicating a downlink component carrier (DL CC) by which downlink data is transmitted, on the basis of a maximum value of the number of DL CCs and of the number of uplink component carriers (UL CCs) being managed in a base station; transmitting the CIF on a 1 st  DL CC to a terminal through a physical downlink control channel (PDCCH); and transmitting downlink data on a 2 nd  DL CC indicated by the CIF to the terminal through a physical downlink shared channel (PDSCH).

TECHNICAL FIELD

The present invention relates to a method and apparatus for transmittingand receiving a control signal in a wireless access system, and moreparticularly, to a method and apparatus for efficiently transmitting andreceiving a control signal in a communication system environment havingcarrier mergence applied thereto.

BACKGROUND ART

Generally, when a packet is transmitted in a mobile communicationsystem, a receiver should inform a transmitter of a success or failurein packet reception. If the packet reception is successful, the receivertransmits ACK to enable the transmitter to transmit a new packet. If thepacket reception is not successful, the receiver transmits NACK toenable the transmitter to retransmit the corresponding packet. Thisoperation may be called ARQ (automatic request).

This ARQ operation may be combined with a channel coding scheme. Inparticular, the above-mentioned ARQ has been proposed as HARQ (hybridARQ) for raising system efficiency by lowering an error rate in a mannerof combining a retransmitted packet with a previously received packet.In order to raise system throughput, the HARQ is requested to receive aACK/NACK response from the receiver quicker than that of the ARQoperation. Hence, ACK/NACK in HARQ is transmitted by physical channelsignaling.

Implementation of HARQ may be mainly into two types. A first type ofHARQ implementation is CC (chase combining). In particular, when aretransmission is performed, a retransmitted packet is transmitted in amanner of having the same code bits using the same modulation scheme ofa previously transmitted packet and the same coding rate of thepreviously transmitted packet. A second type of HARQ is IR (incrementalredundancy). In particular, when a retransmission is performed, atransmission of code bits different from those of a previouslytransmitted packet is granted using a modulation scheme and coding ratedifferent from those of the previously transmitted packet. In this case,a receiver may be able to raise system throughput by coding diversity.

In a multicarrier cellular mobile communication system, user equipmentsbelonging to one or plural cells perform uplink (UL) data packettransmissions to a base station. Since a plurality of user equipmentsare able to transmit UL data packets in a single subframe, a basestation needs to transmit ACK/NACK signals to a plurality of the userequipments in a single subframe as well. In particular, in 3GPP LTEsystem, a base station transmits ACK/NACK signals to a plurality of userequipments on a physical HARQ (hybrid ARQ) indicator channel(hereinafter abbreviated PHICH), i.e., a channel for carrying downlink(DL) ACK/NACK information for UL HARQ.

When a plurality of ACK/NACK signals transmitted by a base station touser equipments in a single subframe are multiplexed by CDMA in apartial time-frequency domain of a DL transmission band of amulticarrier system, they are discriminated from ACK/NACK signals forother user equipments by an orthogonal code or a pseudo orthogonal codemultiplied in a time-frequency domain. Moreover, when QPSK transmissionis performed, they may be divided into two different orthogonal phasecomponents. In particular, in 3GPP LTE system, a plurality of ACK/NACKsignals are transmitted on a plurality of PHICHs by being multiplexed byCDMA. In doing so, a unit of a multiplexed transmission by CDMA iscalled a PHICH group.

Meanwhile, in case that a specific user equipment attempts an initialaccess to a prescribed cell, it is necessary for the specific userequipment to acquire system information. Such a basic information in thesystem information as a system bandwidth and the like may be received ona physical broadcast channel (hereinafter abbreviated PBCH). Yet, inorder to acquire detailed system information in the system informationof a corresponding cell, it may be necessary for a user equipment toreceive a physical downlink shared channel (hereinafter abbreviatedPDSCH) for carrying general DL data.

In doing so, since scheduling information of PDSCH is carried on PDCCHof each subframe, a user equipment in the course of an initial accessreceives PBCH and then receives PDCCH of a specific subframe torecognize scheduling information on PDSCH for carrying detailed systeminformation through the specific subframe. In particular, in order toreceive the PDCCH having the scheduling information on the PDDSCH forcarrying the detailed system information, the user equipment should beaware of a transmission position of the corresponding PDCCH.

Since PDCCH is generally mapped to a resource element (hereinafterabbreviated RE) except resource elements for carrying PHICH and othercontrol signals, the user equipment should be aware how the PHICH andother control signals are mapped to a resource region, in order toreceive the PDCCH.

DISCLOSURE OF THE INVENTION Technical Problem

The object of the present invention is to provide a method and apparatusfor transmitting a control signal.

Another object of the present invention is to provide a method andapparatus for transmitting a control signal in an asymmetricmulticarrier environment.

A further object of the present invention is to provide a method andapparatus for allocating DL CC and/or UL CC to a user equipment in anasymmetric multicarrier environment.

Technical tasks obtainable from the present invention are non-limitedthe above mentioned effect. And, other unmentioned technical tasks s canbe clearly understood from the following description by those havingordinary skill in the technical field to which the present inventionpertains.

Technical Solution

Accordingly, embodiments of the present invention are directed tomethods and apparatuses for transmitting and receiving a control signalin a wireless access system, and more particularly, to methods andapparatuses for transmitting and receiving a control signal (e.g., PDCCHsignal) in an asymmetric multicarrier environment.

According to one embodiment of the present invention, a method oftransmitting a control signal for asymmetric multicarrier in a wirelessaccess system may include the steps of configuring a physical downlinkcontrol channel (PDCCH) signal including a carrier indicator field (CIF)indicating a downlink component carrier (DL CC) carrying downlink data,transmitting the PDCCH signal to a user equipment through a first DL CC,and transmitting the downlink data on a second DL CC indicated by theCIF to the user equipment through a physical downlink shared channel(PDSCH). In this case, the CIF may be determined based on a maximumvalue of the number of downlink component carriers (DL CCs) and thenumber of uplink component carriers (UL CCs) managed by the wirelessaccess system (e.g., LTE-A system). And, the CIF may be included at afixed position previously set irrespective of a type of a payload DCIformat of the PDCCH.

According to another embodiment of the present invention, a method ofreceiving a control signal for asymmetric multicarrier in a wirelessaccess system may include the steps of receiving a carrier indicatorfield (CIF) indicating a second downlink component carrier (DL CC)carrying downlink data on a first DL CC through a physical downlinkcontrol channel (PDCCH) and receiving the downlink data on the second DLCC indicated by the CIF through a physical downlink shared channel(PDSCH). In this case, a size of the CIF is determined based on amaximum value of the number of downlink component carriers (DL CCs) andthe number of uplink component carriers (UL CCs) managed by the wirelessaccess system (e.g., LTE-A system). And, the CIF may be included at afixed position previously set irrespective of a type of a payload DCIformat of the PDCCH.

Moreover, a user equipment may detect PDCCH transmitted to the userequipment by performing blind decoding on PDCCH candidates in aUE-specific search space and a common search space in the first DL CCand may obtain the CIF included in the corresponding PDCCH. The CIF maybe included at a fixed position of the PDCCH payload with a fixed value.

According to another embodiment of the present invention, a basestation, which transmits a control signal for asymmetric multicarrier ina wireless access system, may include a transmitting module configuredto transmit a radio signal, a receiving module configured to receive aradio signal, and a processor configured to control a transmission ofthe control signal by controlling the transmitting module and thereceiving module. In this case, the process may control the steps ofconfiguring a physical downlink control channel (PDCCH) signal includinga carrier indicator field (CIF) indicating a downlink component carrier(DL CC) carrying downlink data, transmitting the PDCCH signal to a userequipment through a first DL CC, and transmitting the downlink data on asecond DL CC indicated by the CIF to the user equipment through aphysical downlink shared channel (PDSCH). In this case, the CIF may bedetermined based on a maximum value of the number of downlink componentcarriers (DL CCs) and the number of uplink component carriers (UL CCs)managed by the wireless access system (e.g., LTE-A system). And, the CIFmay be included at a fixed position previously set irrespective of atype of a payload DCI format of the PDCCH.

According to a further embodiment of the present invention, a userequipment, which receives a control signal for asymmetric multicarrierin a wireless access system, may include a transmitting moduleconfigured to transmit a radio signal, a receiving module configured toreceive a radio signal, and a processor configured to control atransmission of the control signal by controlling the transmittingmodule and the receiving module. In this case, the processor may controlthe steps of receiving a carrier indicator field (CIF) indicating asecond downlink component carrier (DL CC) carrying downlink data on afirst DL CC through a physical downlink control channel (PDCCH) andreceiving the downlink data on the second DL CC indicated by the CIFthrough a physical downlink shared channel (PDSCH). In this case, a sizeof the CIF is determined based on a maximum value of the number ofdownlink component carriers (DL CCs) and the number of uplink componentcarriers (UL CCs) managed by the wireless access system (e.g., LTE-Asystem). And, the CIF may be included at a fixed position previously setirrespective of a type of a payload DCI format of the PDCCH.

According to embodiments of the present invention, the CIF may betransmitted in a manner of being fixed to front part, a rear part or aprescribed position of the payload of the PDCCH. Moreover, if themaximum value of the number of the downlink component carriers (DL CCs)and the number of the uplink component carriers (UL CCs) is 5, it may bepreferable that the size of the CIF is 3 bits.

The above-described embodiments of the present invention are just partsof preferred embodiments of the present invention. And, variousembodiments reflecting the technical features of this invention can bederived and understood by those skilled in the art based on the detaileddescription of the present invention.

Advantageous Effects

Accordingly, the present invention may provide the following effectsand/or advantages.

First of all, a control signal can be transmitted and receivedaccurately and efficiently.

Secondly, a base station may be able to clearly allocate DL CC and/or ULCC for transmitting and receiving data in an asymmetric multicarrierenvironment to a user equipment.

Thirdly, as a control signal is transmitted and received in anasymmetric multicarrier environment, a user equipment is able toaccurately transmit and receive DL data or UL data on DL CC and UL CCindicated by the control signal.

Effects obtainable from the present invention are non-limited the abovementioned effect. And, other unmentioned effects can be clearly derivedand understood from the following description by those having ordinaryskill in the technical field to which the present invention pertains.Namely, unintended effects attributed to implementation of thisinvention can be clearly derived from embodiments of the presentinvention by those having ordinary skill in the technical field to whichthe present invention pertains.

DESCRIPTION OF DRAWINGS

FIGS. 1(a) and (b) are diagrams of an asymmetric structure of multi-bandradio frequency (RF).

FIG. 2 is a diagram of a structure of a radio frame of type 1.

FIG. 3 is a diagram of a structure of a radio frame of type 2.

FIG. 4 is a diagram of a grid structure of a slot used in embodiments ofthe present invention.

FIG. 5 is a diagram of a control channel region and a data channelregion in a single frame.

FIG. 6 is a diagram of a process for mapping PDCCH to a control channel.

FIG. 7 is a diagram for one example of a search space for performingblind decoding.

FIG. 8 is a diagram of a process for a base station to transmit PDCCHand a process for a user equipment to perform blind coding on PDCCHtransmission candidate positions through CSS and USS according to oneembodiment of the present invention.

FIGS. 9(a), (b) and (c) are diagrams for methods of setting a carrierindicator field according to one embodiment of the present invention.

FIG. 10 is a diagram for one of methods of transmitting a carrierindicator field according to an embodiment of the present invention.

FIG. 11 is a diagram of a signal processing for a user equipment totransmit a UL signal according to an embodiment of the presentinvention.

FIG. 12 is a diagram of a signal processing for a base station totransmit a DL signal according to an embodiment of the presentinvention.

FIG. 13 is a diagram of a mobile station and a base station according toan embodiment of the present invention to implement the embodiments ofthe present invention described with reference to FIGS. 5 to 12.

MODE FOR INVENTION

Embodiments of the present invention are directed to methods andapparatuses for transmitting and receiving a control signal in awireless access system, and more particularly, to methods andapparatuses for transmitting and receiving a control signal (e.g., PDCCHsignal) in an asymmetric multicarrier environment.

The following embodiments correspond to combinations of elements andfeatures of the present invention in prescribed forms. And, it may beable to consider that the respective elements or features are selectiveunless they are explicitly mentioned. Each of the elements or featurescan be implemented in a form failing to be combined with other elementsor features. Moreover, it may be able to implement an embodiment of thepresent invention by combining elements and/or features together inpart. A sequence of operations explained for each embodiment of thepresent invention may be modifiable. Some configurations or features ofone embodiment can be included in another embodiment or can besubstituted for corresponding configurations or features of anotherembodiment.

In the description of the drawings, procedures or steps, which may ruinthe substance of the present invention, are not explained. And,procedures or steps, which can be understood by those skilled in theart, are not explained as well.

In this disclosure, embodiments of the present invention may bedescribed centering on the data transmission/reception relations betweena base station and a mobile station. In this case, the base station maybe meaningful as a terminal node of a network which directly performscommunication with the mobile station. In this disclosure, a specificoperation explained as performed by a base station can be performed byan upper node of the base station in some cases.

In particular, in a network constructed with a plurality of networknodes including a base station, it is apparent that various operationsperformed for communication with a mobile station may be performed by abase station or other networks except the base station. In this case,‘base station’ can be replaced by such a terminology as a fixed station,a Node B, an eNode B (eNB), an advanced base station (ABS), an accesspoint and the like.

And, ‘mobile station (MS)’ can be replaced by such a terminology as auser equipment (UE), a subscriber station (SS), a mobile subscriberstation (MSS), an advanced mobile station (AMS), a mobile terminal andthe like.

Moreover, a transmitting end may mean a fixed and/or mobile node thattransmits a data service or an audio service. And, a receiving end maymean a fixed and/or mobile node that receives a data service or an audioservice. Hence, a mobile station can become a transmitting end and abase station can become a receiving end, in uplink. Likewise, a mobilestation becomes a receiving end and a base station can become atransmitting end, in downlink.

Embodiments of the present invention may be supportable by standarddocuments disclosed in at least one of wireless access systems includingIEEE 802.xx system, 3GPP system, 3GPP LTE system and 3GPP2 system. Inparticular, the steps or parts, which are not explained to clearlyreveal the technical idea of the present invention, in the embodimentsof the present invention can be supported by the above documents.Moreover, all terminologies disclosed in this document may besupportable by the above-mentioned standard documents.

In the following description, a preferred embodiment of the presentinvention is explained in detail with reference to the accompanyingdrawings. Detailed description disclosed together with the accompanyingdrawings is intended to explain not a unique embodiment of the presentinvention but an exemplary embodiment of the present invention.

In the following description, specific terminologies used forembodiments of the present invention may be provided to help theunderstanding of the present invention. And, the use of the specificterminology may be modified into another form(s) within the scope of thetechnical idea of the present invention.

FIGS. 1(a) and (b) is a diagram of an asymmetric structure of multi-bandradio frequency (RF).

In order to efficiently use a multicarrier (or multiband), one MAC(medium access control) entity has been proposed to manage severalcarriers (e.g., several FA (frequency allocation) bands).

A Mac layer included in each of a transmitting end and a receiving endmay be able to manage several carriers to efficiently use amulticarrier. In this case, in order to effectively transmit and receivethe multicarrier, assume that each of the transmitting end and thereceiving end may be able to transmit and receive multicarriers.

Since frequency carriers (FCs) managed by one MAC layer need not becontiguous to each other, it may be flexible in aspect of resourcemanagement. In particular, one MAC entity may be able to manage bothcontiguous aggregation of carriers situated contiguous with each other,and non-contiguous aggregation of carriers situated non-contiguous witheach other.

Referring to FIG. 1, FIG. 1(a) shows an asymmetric multicarrierstructure in which the number of downlink component carriers (DL CCs)allocated to a mobile station is greater than that of uplink componentcarriers (UL CCs). And, FIG. 1(b) shows an asymmetric multicarrierstructure in case that the number of DL CCs allocated to a mobilestation is smaller than that of UL CCs.

In the following description, a frame structure for transmitting andreceiving radio signals used in embodiments of the present invention isexplained.

FIG. 2 is a diagram of a structure of a radio frame of type 1. And, FIG.3 is a diagram of a structure of a radio frame of type 2.

In a cellular OFDM radio packet communication system, UL/DL data packettransmission may be performed by subframe unit. In this case, onesubframe may be defined as a predetermined time interval including aplurality of OFDM symbols.

The 3GPP (₃rd generation partnership project) supports a radio (orwireless) frame structure of type 1 applicable to FDD (frequencydivision duplex) and a radio frame structure of type 2 applicable to TDDtime division duplex).

A type-1 radio frame configured with 10 subframes. And, 1 subframeincludes 2 slots. A type-2 radio frame configured with 2 half frames.And, each half frame includes subframes, DwPTS (downlink piloting timeslot), GP (gap period) and UpPTS (uplink piloting time slot). In thiscase, 1 subframe includes 2 slots. In particular, 1 subframe may include2 slots irrespective of a type of a radio frame.

FIG. 4 is a diagram of a grid structure of a slot used in embodiments ofthe present invention.

Referring to FIG. 4, a resource grid in one slot may include N^(DL)_(RB)×N^(RB) _(SC) subcarriers and N^(DL) _(symb) OFDM symbols. In thiscase, the N^(DL) _(RB) indicates the number of resource blocks (RBs) inDL, the N^(RIB) _(SC) indicates the number of subcarriers configuring asingle RB, and the N^(DL) _(symb) indicates the number of OFDM symbolsin a DL slot.

In FIG. 4, a smallest unit of radio resource is a resource element (RE).One RE may be defined as 1 subcarrier and 1 OFDM symbol. And, oneresource block (RB) may include N^(RB) _(SC) subcarriers and N^(DL)_(symb) OFDM symbols.

The RB may be used to describe a mapping relation between a prescribedphysical channel and a prescribed resource element. The RB can bedivided into a physical resource block (PRB) and a virtual resourceblock (VRB). The mapping relation between the VRB and the PRB may bedescribed by 1 subframe unit or each slot unit configuring 1 subframe.And, the mapping relation between the VRB and the PRB may be describedusing the mapping relation between an index of the VRB and an index ofthe PRB.

FIG. 5 is a diagram of a control channel region and a data channelregion in a single frame.

Referring to FIG. 5, resource regions in LTE system may be divided intoa control region (n OFDM symbols, where n 3) and a data region. In thiscase, a control channel may be assigned to the control region and a datachannel may be assigned to a data region.

The control region in DL may start with a 1^(st) OFDM symbol of asubframe and may include at least one OFDMA symbol. A size of thecontrol region may be independently set per subframe. The control regionmay be used to transmit L1/L2 (layer 1/layer 2) control signal. And, thedata region may be used to transmit DL traffic.

Control channels assigned to the control region may include PCFICH(Physical Control Format Indicator CHannel), PHICH (Physical Hybrid-ARQIndicator CHannel), PDCCH (Physical Downlink Control CHannel) and thelike.

PDCCH may be assigned to first n OFDM symbols of a subframe. In thiscase, ‘n’ is an integer equal to or greater than 1 and may be indicatedby PCFICH. The PDCCH may include at least one control channel elements(CCEs). Each CCE includes 9 REGs. Each REG may include 4 neighborresource elements (REs) in a state that a reference signal is excluded.And, the RE is a minimum resource unit defined as 1 subcarrier×1 symbol(cf. FIG. 4).

A base station may inform each user equipment or a user equipment groupof information related to resource allocation of such a transportchannel as a paging channel (PCH) and a downlink-shared channel(DL-SCH), a DL scheduling grant, a UL scheduling grant, informationrelated to HARQ and the like via PDCCH.

The PCH and the DL-SCH are carried on PDSCH. Information indicating thatdata of PDSCH will be transmitted to which user equipment (one or pluraluser equipments), information (i.e., DL grant) indicating how userequipments receive and decode PDSCH data and the like may be transmittedby being contained in the PDSCH.

For instance, assume that a specific PDCCH is CRC (Cyclic RedundancyCheck)-masked with RNTI (radio network temporary identity) named ‘A’ andthat information on data transmitted using a radio resource (e.g.,frequency position) named ‘B’ and transmission format information (e.g.,transport block size, modulation scheme, coding information, etc.) named‘C’ is transmitted via specific subframe. In this case, a user equipmentof a corresponding cell may monitor the PDCCH using RNTI informationpossessed by itself, a user equipment having the RNTI ‘A’ may receivethe PDCCH, and the user equipment may be able to receive PDSCH indicatedby ‘B’ and ‘C’ through the information of the received PDCCH.

FIG. 6 is a diagram of a process for mapping PDCCH to a control channel.

In the following description, PDCCH may be explained in detail. First ofall, a base station may be able to transmit resource allocation andtransmission format (e.g., DL grant) information of PDSCH, resourceallocation information (i.e., UL grant) of physical UL shared channel(PUSCH), activation information on aggregation of transmit power controlcommands for individual user equipments in a random user equipment groupand VoIP (voice over internet protocol) and the like to a user equipmenton PDCCH.

A plurality of PDCCHs may be transmittable within a control region and auser equipment may be then able to monitor a plurality of the PDCCHs.PDCCH may include aggregation of at least one or more contiguous controlchannel elements (CCEs). After subblock interleaving has been performedon the PDCCH including the aggregation of the at least one or morecontiguous CCEs, the corresponding PDCCH may be transmitted via acontrol region.

CCE is a logical allocation unit used to provide a coding rate to PDCCHaccording to states of radio channel. The CCE may correspond to aplurality of resource element groups. In accordance with correlationbetween the number of CCEs and a coding rate provided by the CCEs, aformat of the PDCCH and the number of bits allocated to the PDCCH may bedetermined. Moreover, control information carried on PDCCH may be calleddownlink control information (DCI).

Table 1 shows DCI format.

TABLE 1 DCI format Contents DCI format 0 used for the scheduling ofPUSCH DCI format 1 used for the scheduling of one PDSCH codeword DCIformat used for the compact scheduling of one PDSCH 1A codeword andrandom access procedure initiated by a PDCCH order DCI format used forthe compact scheduling of one PDSCH 1B codeword with precodinginformation DCI format used for very compact scheduling of one PDSCH 1Ccodeword DCI format used for the compact scheduling of one PDSCH 1Dcodeword with precoding and power offset information DCI format 2 usedfor scheduling PDSCH to UEs configured in closed-loop spatialmultiplexing mode DCI format used for scheduling PDSCH to UEs configured2A in open-loop spatial multiplexing mode DCI format 3 used for thetransmission of TPC commands for PUCCH and PUSCH with 2-bit poweradjustments DCI format used for the transmission of TPC commands for 3APUCCH and PUSCH with single bit power adjustments DCI format TBD xx

Referring to Table 1, DCI format 0 indicates UL resource allocationinformation, each of DCI format 1 and DCI format 2 indicates downlinkresource allocation information, and each of DCI format 3 and DCI format3A indicates UL TPC (transmit power control) command for random UEgroups. Moreover, DCI format xx is the DCI format newly defined by thepresent invention and may be used to transmit a carrier indicator fieldexplained in the following description later.

Referring to FIG. 6, a base station (e Node-B) may be able to configurea modulated symbol by performing encoding (e.g., tail biting convolutioncoding), rate matching and modulation (e.g., QPSK) on information bitsaccording to DCI format to transmit to a user equipment. In this case,according to embodiments of the present invention, the modulated symbolmay be called a resource element (RE). And, one REG may be constructedwith 4 REs. Moreover, one CCE may be constructed with 9 REGs.

In order to configure one PDCCH, it may be able to use CCEs amounting tothe number of {1, 2, 4, 8}. In this case, the {1, 2, 4, 8} may be calleda CCE aggregation level. The PDCCH including the CCEs may be interleavedby REG unit and a cyclic shift based on a cell ID may be then performedthereon. The PDCCH may be then mapped to a physical resource.

In LTE system, a user equipment may not be aware that PDCCH signalstransmitted by a base station are transmitted using a prescribed CCEaggregation level or a prescribed DCI format at a prescribed position.Hence, the user equipment may perform blind decoding to receive thePDCCH signal from the base station.

The blind coding is a scheme of checking whether a received PDCCH is acontrol channel of the user equipment in a manner of de-masking its ID(e.g., UE ID) from a CRC (Cyclic Redundancy Check) part of the receivedPDCCH and then checking a corresponding CRC. In LTE, a concept of asearch space, as shown in FIG. 7, is defined in LTE to perform the blinddecoding.

FIG. 7 is a diagram for one example of a search space for performingblind decoding.

Referring to FIG. 7, a search space may be classified into a commonsearch space (CSS) and a user equipment-specific search space (USS). Inparticular, the CSS may be constructed with 16 CCEs corresponding to CCEindexes 0 to 15, respectively. And, the CSS may be able to support PDCCHhaving a CCE aggregation level of {4, 8}. Meanwhile, the UCC may beconstructed with 16 CCEs corresponding to CCE index regions 0 to Ncce-1,respectively. And, the USS may be able to support PDCCH having a CCEaggregation level of {1, 2, 4, 8}. If the CCE indexes of the USS range 0to Ncce-1, whereas the CCE indexes of the CSS range 0 to 15, it may meanthat the CSS and the USS may overlap with each other.

A user equipment may perform blind decoding to find its PDCCH based onthe CCE aggregation level within the USS and its UE (user equipment) ID.In particular, the user equipment may calculate a starting point of theUSS, on which the blind decoding will be initially performed, using theUE ID and the CCE aggregation level. In this case, if the starting pointbelongs to a range of the CCE indexes 0 to 15, it may configure the USSoverlapping with the CSS.

Table 2 shows one example of a search space configuration.

TABLE 2 Search space S_(k) ^((L)) Number of Aggregation Size [in PDCCHDCI Type level L CCEs] candidates M^((L)) formats UE- 1 6 6 0, 1, 1A,specific 2 12 6 1B, 2 4 8 2 8 16 2 Common 4 16 4 0, 1A, 8 16 2 2C, 3/3A

Referring to Table 2, USS may have 6 PDCCH candidates for each of CCEaggregation level 1 and CCE aggregation level 2 and may also have 2PDCCH candidates for each of CCE aggregation level 4 and CCE aggregationlevel 8. In this case, DCI format may be selected from 0, 1, 1A, 1B and2. CSS may have 4 PDCCH candidates at the CCE aggregation level 4 or mayhave 2 PDCCH candidates at the CCE aggregation level 8. In this case,DCI format may be selected from 0, 1A, 1C, 3 and 3A.

In the following description, a method of configuring USS based onHashing Function may be explained. In particular, the USS may beconfigured by UE ID, CCE aggregation level and the number of CCEs in acorresponding subframe. And, the USS may be calculated by Formula 1 asfollows.

S _(k) ^((L)) =L·{(Y _(k)+mod)mod└N _(CCE,k) /L┘}+i

Y _(k)=(A·Y _(k−1))mod D   [Formula 1]

In Formula 1, ‘L’ indicates CCE aggregation level, ‘Y_(k)’ is avariable, N_(CCE,k) indicates the number of CCEs, ‘i’ has a range of 0,. . . , L−1, ‘m’ has a range of 0, . . . , M^((L))−1, and ‘M^((L))’indicates the number of PDCCH candidates to be monitored in a givensearch space. Moreover, it is ‘Y⁻¹=n_(RNTI)=!0’, it is ‘A=39827’, it is‘D=65537’, and it is k=└n_(s)/2┘. Moreover, ‘n_(s)’ indicates a slotnumber in a radio frame.

A user equipment may be able to perform blind decoding on PDCCH transmitcandidate positions defined per individual CCE aggregation level in areceived CCE column through CSS and USS.

In particular, the count of PDCCH blind decodings, which can beperformed by an LTE UE in DL subframe to the maximum, may become 44. Forinstance, as described in Table 2, a UE may be able to perform 4 PDCCHblind decodings for CCE aggregation level 4, and 2 PDCCH blind decodingsfor CCE aggregation level 8 on the PDCCH format having two kinds ofdifferent DCI (download control information) payloads in CSS.

And, the UE may be able to perform 6 PDCCH blind decodings for CCEaggregation level 1, 6 PDCCH blind decodings for CCE aggregation level2, 2 PDCCH blind decodings for CCE aggregation level 4 and 2 PDCCH blinddecodings for CCE aggregation level 8 on 2 kinds of PDCCH formats havingDCI payloads differing from each other in DL scheduling grant and ULscheduling grant through USS. Hence, the user equipment may be able toperform total 44(=2*6+2*16) PDCCH blind decodings.

Carrier Indicator Field (CIF) And Payload Fixing Method

Unlike LTE Release 8 system or LTE Release 9 system, LTE-A system mayconfigure a plurality of component carriers (CCs) situated contiguous orseparate with frequency resource or may assign the component carriers toLTE-A user equipment.

LTE-A system may enable a plurality of carriers, which are set in arandom transmission subframe, to simultaneously carry a physical controlchannel and a physical data shared channel through transmission schemesetting and resource allocation by a base station scheduler. This may becalled carrier aggregation.

In the LTE-A system, the carrier aggregation may be individuallyapplicable to DL carriers and UL carriers in FDD mode. In case of thecarrier aggregation, a random LTE-A base station may differentiate thenumber of carriers set to transmit physical channel signals to a randomLTE-A user equipment in DL and UL through scheduling. This may be namedasymmetric carrier aggregation.

Moreover, the carrier aggregation may be available in TDD mode based onunpaired carriers. If the number of carriers in carrier aggregation inDL subframe is different from the number of carriers in carrieraggregation in UL subframe, it may be called asymmetric carrieraggregation as well.

FIG. 8 is a diagram of a process for a base station to transmit PDCCHand a process for a user equipment to perform blind coding on PDCCHtransmission candidate positions through CSS and USS according to oneembodiment of the present invention.

First of all, LTE-A system may define a physical layer processing and aMAC processing per individual carrier (e.g., component carrier) in caseof carrier aggregation. Referring to FIG. 8, a data packet to betransmitted per individual carrier may be constructed with transportblock in MAC layer of LTE base station (eNB). The transport block may bedelivered to a physical layer via a transport layer. In the physicallayer, an independent baseband processing and a separate IFFT (inversefast Fourier transform) [in case of UL, per-carrier DFT (discreteFourier transform) is defined prior to IFFT] processing may beperformed.

A user equipment (UE) may detect PDCCH through the blind decodingdescribed with reference to FIG. 7 and may be then able to reconstructdata included in the corresponding PDCCH through the operation shown inFIG. 8.

In the following description, when a DL CC carrying PDCCH containing aDL grant message is different from a DL CC carrying a PDSCH signal, amethod of indicating the DL CC carrying the PDSCH signal may beexplained. Moreover, when a UL CC linked to a DL CC carrying PDCCHcontaining a UL grant message is different from a UL CC carrying a PUSCHsignal, a method of indicating the corresponding UL CC may be explained.

First of all, in carrier aggregation environment, a base station may beable to send a DL grant message for scheduling a radio resourceallocated to a user equipment or a UL grant message to the userequipment via prescribed PDCCH. In this case, it may be able to define acarrier indicator field (CIF) to indicate that the corresponding DL orUL grant message is related to a PDSCH transmission on which DL CC orthat the corresponding DL or UL grant message is related to a PUSCHtransmission on which DL CC. In the following description, explained ishow the CIF is transmitted in a payload structure of a controlinformation message of the PDCCH.

Regarding the relation between the DL CC carrying the PDCCH and the DLCC carrying the PDSCH or the UL CC carrying the PUSCH, in case of theasymmetric carrier aggregation, CIF may be transmitted by beingcontained in the PDCCH control information message. In particular, incase of an asymmetric multicarrier environment, in which the number ofDL CCs is greater than that of UL CCs, it may be advantageous for thetransmission of PDCCH containing a random UL grant message to beperformed by one of a plurality of DL CCs in aspect of DL resourceoverhead and UE blind decoding cost. Regarding a method of transmittingthe PDCCH containing the UL grant message, one issued point may relateto how to set one DL CC to transmit the PDCCH containing the UL grantmessage among a plurality of the DL CCs and how a user equipment canidentify a UL grant message for PUSCH transmission of which UL CC inblind-decoding the corresponding PDCCH.

Likewise, in case of an asymmetric multicarrier environment, in whichthe number of DL CCs is smaller than that of UL CCs, a base station maybe able to transmit PDCCHs containing a plurality of UL grants, whichindicate transmissions of PUSCHs on a plurality of UL CCs, to a userequipment in a random DL subframe via random DL CC.

However, in this case, the user equipment may be unable to check the ULCC carrying the corresponding PUSCH from a UL grant message receivedthrough PDCCH blind decoding with UL grant DCI format currently definedin LTE. Therefore, in order to clear this vagueness, a method for ULgrant DCI format to indicate UL CC carrying a corresponding PUSCH may berequired.

Regarding the relation between the DL CC carrying the PDCCH and the DLCC carrying the PDSCH or the UL CC carrying the PUSCH, for anotherexample of leading to a situation for requiring CIF within a PDCCHcontrol information message, it may be able to apply a configurationoperation of a base station as follows. First of all, DL CC carryingPDCCH including a DL grant message may be intentionally set differentfrom DL CC carrying a PDSCH signal based on a random purpose. Secondly,UL CC linked with DL CC carrying PDCCH including a UL grant message maybe set different from UL CC carrying a PUSCH signal. This may berepresented as cross-carrier scheduling.

Due to a series of DL asymmetric carrier aggregation setting for thecross-carrier scheduling or the cross-carrier scheduling application, adirect solution for the issues caused by the PDSCH transmission for thePDCCH transmission including the DL grant message or the PUSCHtransmission for the PDCCH transmission including the UL grant messagemay include the steps of defining DCI formats of new DL and UL grantmessages including an index of DL CC carrying PDSCH scheduled by a basestation or an index of UL CC carrying PUSCH scheduled by a base stationand then providing them to a user equipment via PDCCH including thesame.

In addition, in order to mitigate the excessive increase of overhead ofPDCCH blind decoding performed by a random LTE-A user equipment due tothe carrier aggregation, in case that a base station transmits PDCCHsincluding a plurality of DL or UL grant messages in a random physicalresource region on which a random user equipment performs PDCCH blinddecoding, it may be able to consider the following transmissions. Firstof all, the transmission may be performed by fixing a size of payload ofall DCI formats for DL grants or UL grants [Case of separate coding].Secondly, a single UL grant may be transmitted irrespective of thenumber of UL CC [Case of joint coding].

According to the present invention, it may be able to newly define acarrier indicator field (CIF) to indicate DL CC carrying PDSCH scheduledthrough a corresponding grant message control information or UL CCcarrying PUSCH on a DL or UL grant message or its DCI format in asituation that the aforesaid asymmetric carrier aggregation or theaforesaid cross-carrier scheduling is applied.

In particular, in case that DL CC carrying PDCCH including a DL grantmessage is different from DL CC carrying PDSCH scheduled through thecorresponding PDCCH, the CIF may be able to indicate the DL CC carryingthe PDSCH. In this case, the CIF may be transmitted in a manner of beingincluded in the DL grant message or PDCCH payload carrying the same.Moreover, in case that UL CC linked with DL CC carrying PDCCH includinga DL grant message is different from UL CC carrying PUSCH scheduledthrough the corresponding PDCCH, the CIF may be able to indicate the ULCC carrying the PUSCH. In this case, the CIF may be transmitted in amanner of being included in the UL grant message or PDCCH payloadcarrying the same.

The CIF may be able to indicate UL CC carrying PUSCH scheduled throughPDCCH irrespective of a position (i.e., carrier index) of transmissionDL CC of the corresponding PDCCH carrying a UL scheduling grant message.And, the CIF may be able to indicate DL CC carrying PDSCH scheduledthrough PDCCH irrespective of a position (i.e., carrier index) of DL CCof the corresponding PDCCH carrying a DL scheduling grant message.

In this case, the CIF may be included in a DCI format for the UL grantmessage or a DCI format for a DL grant message. The DCI format includingthe CIF may be newly defined as a new format or may use the DCI formatsdescribed with reference to Table 1 entirely or in part.

FIG. 9 is a diagram for methods of configuring a carrier indicator fieldaccording to one embodiment of the present invention.

Referring to FIG. 9, CIF may be transmitted at a fixed position of DCIformat payload of PDCCH carrying a random DL or UL grant message. Atransmission mode (e.g., closed-loop/open-loop MIMO precodingtransmission, transmit diversity and/or single/multiple antennatransmission, etc.) applied to PDSCH transmission on a random DL CC inLTE-A or PUSCH transmission on a random UL CC is the informationbasically configured by a base station. In particular, assume that acorresponding transmission mode is previously indicated to a userequipment and that the user equipment is already aware of thecorresponding transmission mode.

A user equipment performs blind decoding on a transmission of PDCCHincluding a DL or UL grant message per transmission mode, performs a CRCerror check, and may be then read a DCI format payload. In this process,it may happen that each of control information messages respectivelyhaving DCI formats different from each other may have the same payloadsize due to such a reason as a difference in condition including acarrier band on DL CC or UL CC and the like.

To cope with this situation, a base station may transmit a CIF to a userequipment by defining the CIF at a fixed position in a PDCCH payloadirrespective of a presence or non-presence of equivalence of a DCIformat, a presence or non-presence of equivalence of a carrier bandand/or a type of DCI format. Hence a user equipment, which is alreadyaware of a transmission mode of individual DL CC and/or UL CC, reads theCIF at the fixed position right after completion of the CRC error checkand may be then obtain the configuration of control information payloadof the rest of the DCI format.

As mentioned in the foregoing description, regarding the methods offixing the position of the CIF, a CIF field may be inserted at a frontpart (e.g., MSB) of PDCCH payload in a fixed size [cf. FIG. 9(a)], maybe inserted at a last part (e.g., LSB) of the PDCCH payload in a fixedsize [cf. FIG. 9(b)], or may be inserted at a prescribed position of thePDCCH payload in a fixed size [cf. FIG. 9(c)].

In this case, the size of the CIF may be determined in a manner of beingfixed on the basis of the number of DL CC and UL CC managed by a basestation. On the other hand, the size of the CIF may be determinedvariably in accordance with the number of DL CC and/or the number of ULCC set for a corresponding user equipment for the purpose oftransmission of PDSCH or PUSCH.

In the following description, a method of setting a size of CIF may beexplained in detail.

First of all, a base station may be able to indicate a component carrier(CC) carrying a PDSCH or PUSCH signal using a CIF in case of applyingcarrier aggregation.

In case that a CIF is included in a DCI format payload of PDCCHincluding a UL or DL grant message, in aspect of optimizing to manage asize of the DCI format payload, a size of the CIF may be preferablydefined as a bit size capable of appropriately representing the numberof DL CC set for a user equipment to receive PDSCH from a base stationand/or the number of UL CC set to transmit PUSCH.

For instance, if the number DL CCs set for a user equipment to receivePDSCH is 2, CIF may be included in a DCI format payload of a DL grantPDCCH in a size of 1 bit. If the number of DL CCs is 4, a 2-bit CIF maybe included in a DCI format payload of a DL grant PDCCH. In particular,if the number of DL CC or UL CC set for a user equipment to receivePDSCH or transmit PUSCH is set to N, it may be able to set a size of aCIF to a minimum number of bits capable of representing the N.

FIG. 10 is a diagram for one of methods of transmitting a carrierindicator field according to an embodiment of the present invention.

Referring to FIG. 10, a base station may be able to determine a size ofCIF included in PDCCH. For instance, the base station may be able todetermine a size of CIF by such a method described with reference toFIG. 9 based on the maximum number of DL CC set for the PDSCHtransmission to a corresponding user equipment and/or the maximum numberof UL CC set for the PUSCH reception [S1010].

In the step S1010, described is the case that the base stationdetermines the size of the CIF. Yet, in another aspect of the presentinvention, a value of the CIF may be determined in accordance with themaximum number of component carriers available for the LTE system. Inthis case, the base station may be able to use a size of the CIFpreviously set by the LTE system irrespective of a DL/UL CC valuemanaged by the base station itself.

The base station eNB may be able to configure PDCCH including thesize-determined CIF. In particular, the base station has the CIFincluded in a preset fixed part of PDCCH payload and may be then able totransmit it to the user equipment UE. In doing so, a position of the CIFassigned to the PDCCH payload may refer to FIG. 9 [S1020].

The user equipment UE may be able to obtain the CIF carried on the PDCCHby performing blind decoding (cf. FIGS. 6 to 8) [S1030].

Finally, the user equipment may be able to receive the PDSCH via the DLCC indicated by the CIF [S1040].

The CIF transmitting method described with reference to FIG. 10 may beidentically applicable to a method of fixing a size and transmissionposition of CIF in case of transmission of PDCCH including a UL grantmessage. Hence, a user equipment may be able to transmit PUSCH via theUL CC indicated by the CIF.

In case that a size of CIF is changed in accordance with the number ofDL CC or UL CC set for a user equipment, a range of a size change of atarget DCI format payload, on which PDCCH blind decoding may beperformed by the user equipment in accordance with a case of a carrierband between individual CCs and a transmission mode configuration of theindividual CC, may be increased. For instance, in case of a size changeof a resource block setting field for a size of a carrier band of aspecific DL or UL CC and a change of UE-specific grant DCI format onPDCCH in accordance with a transmission mode, a size of CIF may bechanged in accordance with the number of DL or UL CC set for acorresponding UE by a base station. This situation may cause an effectthat a range of a change of a whole PDCCH payload is increased. Due tothis situation, it may be advantageous in that a function part ofhandling complicated situations for a PDCCH blind decoding function of auser equipment should be further included or in that complexity andoverhead of the PDCCH blind decoding may be increased.

In consideration of the above disadvantages, the present invention mayadopt a method of a applying a CIF in a manner of fixing a size of theCIF on a DL or UL grant message DCI format for an LTE-A base station toindicate DL/UL CC for PDSC/PUSCH transmission to an LTE-A user equipmenton a system irrespective of the number of DL/UL CCs set for the userequipment by the base station.

In the following description, a method of determining a size of CIFincluded in PDCCH by an LTE system and/or a base station may beexplained, In this case, it may be necessary for the CIF to have thesize enough to indicate DL/UL CCs allocated to a user equipmentsupportive of LTE-A.

A size of CIF applied by a base station and a user equipment in LTE-Asystem may be derived using Formula 2 as follows.

size_of_CIF=┌log, M┐  [Formula 2]

In Formula 2, the M may be set to a maximum value of a maximum number ofDL/UL CC, which can be assigned or configured for a random userequipment by a base station to perform PDCCH/PUSCH transmission oncarrier aggregation in LTE-A system. In particular, a value of the M maybe determined as Max {maximum # of DL CCs settable for a user equipmentby a base station in LTE-A system, maximum # of UL CCs settable for auser equipment by a base station in LTE-A system}. In case that carrieraggregation is applied in LTE-A system, when a base station supportsmaximum 5 of DL CCs assigned or configured for a user equipment, if amaximum number of UL CCs assigned or configured for PUSCH is smallerthan that of the DL CCs, the value of M may be determined as 3 bits byFormula 2.

The CIF, of which size is determined by a random one of theabove-proposed methods, may be defined as a new DCI format in a mannerof being explicitly added to a DCI (downlink control information) formatof DL or UL grant message. Hence, a new DCI format (DCI format xx) isdefined as well as a previously defined DCI format (cf. Table 1) and abase station may be able to transmit a DL or UL grant message includingCIF to a random LTE-A user equipment on PDCCH using the new DCI format.In particular, the CIF may be explicitly added to a DL and/or UL grantDCI format.

According to another proposal of the present invention to have CIFincluded in a random PDCCH DCI format, bits of at least one or morefields among control information fields (cf. Table 1), in which the CIFis designated to a DCI format, may be used entirely or in part as afield for the above-described CIF of the present invention.

For instance, some of CIF bits having randomly fixed sizes and randomlyfixed positions may be transmitted in a manner of being defined as a newfield on an explicitly applied DCI format and the rest of the bits maybe used in a manner that some or all of the bits of the previouslydefined fields are switched. In this case, a previous field considerableto transmit CIF bit or state in a random DCI format may be designated asfollows.

First of all, in case that CIF is used to indicate UL CC carrying arandom PUSCH, padding bits of X bits (X≧1) for a size matching with aseries of DL DCI format in UL grant DCI format [1], 11-bit frequencyhopping indicator [2], spare bits or states in resource assignment (RA)[3], and/or spare bits or states in MCS field [4] may be usable for theCIF.

Secondly, in case that CIF is used to indicate DL CC carrying a randomPDSCH, padding bits of Y bits (Y≧1) for a size matching with a series ofother DL DCI format or UL DCI format in DL grant DCI format [1], sparebits or states in resource assignment (RA) [2], and/or spare bits orstates in MCS field [3] may be usable for the CIF.

When bits corresponding to CIF are newly defined, as mentioned in theforegoing description of the present invention, they may be inserted ata fixed position in a fixed size (cf. FIG. 9) on payload of PDCCH of arandom DCI format. In case that the above-described previous fields areswitched to be used as some or all of CIF bits, it may be able toconsider a method of transmitting the corresponding fields at apreviously defined position. Instead, the fields may be transmitted at afixed position irrespective of DCI format.

In doing so, if a field newly defined for CIF information is applied inthe same manner of a field defined in a previous DCI format, a positionof the newly defined field may be fixed. Moreover, in case that fieldsof a previous DCI format are used as CIF, they can be designated to aprescribed fixed position in a previous DCI format.

According to another embodiment of the present invention, a method oftransmitting CIF may be described as follows. First of all, LTE-A basestation may be able to perform separate coding on a payload part definedseparate from a previous DCI format of PDCCH for a CIF to transmit. Indoing so, CIF assigned position in all DL or UL grant PDCCH payload maybe determined as a position designated when CIF bits are multiplexedwith coded bits or modulation symbols of another DL or UL grant messageinformation in coded bits or their modulation symbols (e.g., QPSK).Moreover, a position on {DCCH payload of CIF coded bit or modulationsymbol may be fixed irrespective of a type of control information of DLor UL grant multiplexed together or a type of DCI format.

For UL/DL grant PDCCHs transmitted by LTE-A base station, a userequipment (UE) may be able to obtain a CIF indicating DL/UL CC carryingPDSCH/PUSCH scheduled for the user equipment from PDCCH received throughblind decoding [cf. FIGS. 6 to 8].

The terminology ‘CIF’ used in the embodiments of the present inventionmay be used as the same meaning of such a terminology as a componentcarrier index (CCI). Occasionally, an index of DL/UL CC indicated viaCIF may be able to use an intact index of CCI uniquely defined inaccordance with the number of DL/UL CC set for a random LTE-A userequipment or a setting situation.

In this case, the CCI may be configured by a base station for thepurpose of indicating DL CC and/or UL CC allocated to a user equipmentfor a case of carrier aggregation and may be then usable by beingconfigured through RRC signaling to the user equipment.

According to embodiments of the present invention, in a situation of anasymmetric multicarrier environment, in which DL CCs are allocated morethan UL CCs, or a cross-carrier scheduling situation, if a UL grantmessage is carried on one DL CC among multiple DL CCs linked to UL CC,it may be more efficient in aspects of DL PDCCH resource overhead andblind decoding costs of a user equipment.

Likewise, if a DL grant message is carried on one DL CC for PDSCHtransmission on a random DL CC, it may be more efficient in aspects ofDL PDCCH resource overhead and blind decoding costs of a user equipment.Moreover, in an asymmetric multicarrier environment having UL CCsallocated more than DL CCs, a method of indicating a UL CC using CIF maybe required for eliminating unclearness of DL CC identification on a ULgrant message.

UL ACK/NACK Transmitting Method

In the following description, a method of transmitting UL ACK/NACK (A/N)is explained.

In an asymmetric multicarrier structure in which the number of DL CC isgreater than that of UL CC, in case of generating transport block (TB)per component carrier, LTE-A user equipment may have to transmitmultiple A/N information corresponding to PDSCH on UL CC. In this case,a user equipment may be able to consider a UL A/N design such as amethod of transmitting multiple A/N feedback for each UL CC [1] or amethod of transmitting one bundled A/N for each UL CC [2].

In doing so, the multiple A/N transmission may be configured usingmultiple A/N PUCCH, channel selection, high order modulation and jointcoding scheme. Moreover, the bundled A/N transmission may be based onHARQ bundling for multiple DL CCs linked with UL CC.

At least, in case of a non-power limited UE situated at a central partof a cell, if A/N bundled die to DTX detection problem and overhead ofretransmission via bundling is transmitted, it may be inappropriate inaspect of UL resource utilization. Hence, in case of a UE situated at acell center, a multiple A/N transmitting method may be more appropriatethan an A/N bundling scheme.

A UL A/N resource allocating method for a scheduled PDSCH transmissionmay be close relation to a UL A/N design problem and a problem ofbackward compatibility of LTE Rel-8 user equipment with a previoussystem.

In an asymmetric multicarrier structure, in which the number of UL CC isgreater than that of DL CC, it may be able to use multiple UL CCs for ULA/N transmission. In this case, in aspect of UL resource utilization, itmay be preferable that UL A/N corresponding to PDSCH is carried on oneUL CC.

In particular, in an asymmetric multicarrier environment in which DL CCexist more than UL CC, in case of a non-power limited UE, multiple A/Nfeedback in each UL CC is more efficient than A/N bundling. In anasymmetric multicarrier environment in which DL CC exist less than ULCC, it may be necessary to further define the DL/UL linkage betweenPDSCH transmission and UL A/N feedback.

DL ACK/NACK Transmitting Method

A method of transmitting DL ACK/NACK (A/N) is explained.

In an asymmetric multicarrier environment in which DL CCs are allocatedmore than UL CC, DL A/N transmission for PUSCH may be preferablyperformed on one DL CC among multiple DL CCs linked to UL CC in a mannersimilar to that of UL grant transmission. A resource (i.e., PHICH group)for DL A/N in each DL CC may be determined in accordance with the numberof DL RB and a scale parameter. Hence, multiple DL A/N may betransmitted on multiple DL CCs for PUSCH transmission.

A method of selecting DL CC used for DL A/N transmission may bedescribed as follows. First of all, if DL CC is selected, it may beperformed based on an existence of non-PHICH DL CC and selection of DLCC for UL grant PDCCH transmission. In particular, DL A/N correspondingto PUSCH may be transmitted on a reference carrier used for UL granttransmission. Hence, the reference carrier may be usable for DL A/Ntransmission.

In an asymmetric multicarrier environment in which more UL CCs areallocated than DL CCs, multiple DL A/N transmission or DL A/N bundlingmay be taken into consideration in case of transmitting a plurality ofPUSCHs on UL CC linked to DL CC. In this case, in aspect of throughputloss, multiple A/N transmission is more efficient than A/N bundling.Yet, the A/N bundling may be considered to maintain the current LTERel-8 PHICH design.

Therefore, in an asymmetric multicarrier environment in which more DLCCs exist than UL CCs, DL A/N for PUSCH transmission may be preferablytransmitted on one DL CC used for UL grant transmission. Moreover, in anasymmetric multicarrier environment in which more UL CCs exist than DLCCs, in case of transmission of multiple PUSCH on UL CC linked to DL CC,it may be able to consider multiple DL A/N or A/N bundling.

FIG. 11 is a diagram of a signal processing for a user equipment totransmit a UL signal according to an embodiment of the presentinvention.

Referring to FIG. 11, a scrambling module 1110 of a user equipment mayscramble a transmitted signal to transmit a UL signal using aUE-specific scrambling signal. The scrambled signal may be inputted to amodulation mapper 1120 and may be then modulated into a complex symbolby BPSK, QPSK or 16 QAM in accordance with a type of the transmittedsignal and/or a channel status. Thereafter, the modulated complex symbolmay be spread by a transform precoder 1130 corresponding to DFTspreading and may be then inputted to a resource element mapper 1140.The resource element mapper 1440 may be then able to map the complexsymbol to a time-frequency resource element to be used for realtransmission. The above-processed signal may enter an SC-FDAM signalgenerator 1150 and may be then transmitted to a base station via anantenna.

In particular, a user equipment may generate radio signals through thesignal processing described with reference to FIG. 11 and may be thenable to transmit the radio signals to a base station on UL channels. Forinstance, a user equipment performs signal processing on input data andthen transmits the corresponding data on PUSCH. Alternatively, a userequipment may be able to transmit A/N signals to a base station by thesignal processing described with reference to FIG. 11. The base stationmay be then able to obtain the corresponding UL signals by inverselyperforming the signal processing described with reference to FIG. 11.

FIG. 12 is a diagram of a signal processing for a base station totransmit a DL signal according to an embodiment of the presentinvention.

Referring to FIG. 12, a base station in 3GPP LTE system may be able totransmit at least one code word in DL. Hence, the at least one code wordmay be processed into a complex symbol via a scrambling module 1210 anda modulation mapper 1220 like the UL shown in FIG. 11. Thereafter, thecomplex symbol may be mapped to a plurality of layers by a layer mapper1230 and each of the layers may be assigned to each transmitting antennaby being multiplied by a prescribed precoding matrix in accordance witha channel status by a precoding module 1240. The above-processedtransmitted signal per antenna may be mapped to a time-frequencyresource element to be used for a transmission by a correspondingresource element mapper 1250, may enter an OFDM signal generator 1260,and may be then transmitted via each antenna. A base station maygenerate radio signals through the signal processing described withreference to FIG. 12 and may be then able to transmit the radio signalsto a user equipment on DL channels.

In particular, a base station may generate radio signals through thesignal processing described with reference to FIG. 12 and may be thenable to transmit the radio signals to a user equipment on DL channels.For instance, a base station performs signal processing on input dataand then transmits the corresponding data on PDCCH or PDSCH or maytransmit A/N signals to a user equipment by the signal processingdescribed with reference to FIG. 12. In particular, the base station maybe able to transmit the PDCCH signal described with reference to FIG. 8using the components described with reference to FIG. 12. Moreover, auser equipment may be able to obtain the corresponding DL signals byinversely performing the signal processing described with reference toFIG. 12.

FIG. 13 is a diagram of a mobile station and a base station according toan embodiment of the present invention to implement the embodiments ofthe present invention described with reference to FIGS. 5 to 12.

First of all, a mobile station may operate as a transmitter in uplink ormay operate as a receiver in downlink. A base station may operate as areceiver in uplink or may operate as a transmitter in downlink.

In particular, the mobile station may include a transmitting module (Txmodule) 1340 and a receiving module (Rx module) 1360 to controltransmission and reception of information, data and/or message. The basestation may include a transmitting module (Tx module) 1350 and areceiving module (Rx module) 1370 to control transmission and receptionof information, data and/or message. The mobile and base stations caninclude antennas 1300 and 1310 to receive information, data and/ormessages, respectively. Moreover, the mobile and base stations caninclude processors 1320 and 1330 for performing embodiments of thepresent invention and memories 1380 and 1390 for storing processingprocedures of the processors temporarily or permanently, respectively.

The transmitting and receiving modules included in the mobile/basestation may perform a packet modulation/demodulation function for datatransmission, a fast packet channel coding function, an OFDMA(orthogonal frequency division multiple access) packet schedulingfunction, a TTD (time division duplex) packet scheduling function and/ora channel multiplexing function.

Moreover, the processor of the base station may be able to determine asize of CIF, as shown in FIG. 10, based on DL CC and UL CC managed bythe base station. For instance, in accordance with a maximum number ofcomponent carriers possibly allocated to the mobile station, the basestation may be able to determine the size of the CIF. Of course, it maybe able to determine the size of the CIF with the maximum number ofcomponent carriers supportable in a corresponding wireless accesssystem. Moreover, the processor of the base station may control thetransmitting module to transmit the PDCCH including the CIF and PDSCH tothe mobile station by the signal processing described with reference toFIG. 11.

The processor of the mobile station may be able to control the receivingmodule to receive the PDSCH on the DL CC indicated by the CIF. Forinstance, in case of DL scheduling, the processor of the mobile stationmay control the receiving module to detect a PDCCH candidate in a searchspace by blind decoding [cf. FIGS. 6 to 8] and may be aware of the DL CCcarrying the PDSCH by obtaining the CIF included in the detected PDCCH.Therefore, the mobile station may be able to receive the PDSCH on thecorresponding DL CC.

In case of UL scheduling, the mobile station may control the receivingmodule to detect a PDCCH candidate in a search space by blind decoding[cf. FIGS. 6 to 8] and may be aware of the UL CC to carry PUSCH byobtaining the CIF included in the detected PDCCH. Therefore, the mobilestation may be able to transmit a PUSCH signal to the base station onthe corresponding UL CC.

Meanwhile, in the present invention, a mobile station may include one ofa personal digital assistant (PDA), a cellular phone, a personalcommunication service (PCS) phone, a GSM (global system for mobile)phone, a WCDMA (wideband CDMA) phone, an MBS (mobile broadband system)phone, a hand-held PC, a notebook PC, a smart phone, a MM-MB(multimode-multiband) terminal and the like.

In this case, the smart phone is a terminal provided with advantages ofa mobile communication terminal and a PDA. The smart phone may mean aterminal in which a schedule management function of a PDA, datacommunication functions of fax transmission/reception, internet access,etc. are integrated on a mobile communication terminal. And, amultimode-multiband terminal means a terminal having a built-inmulti-MODEM chip to be operable in a portable internet system and othermobile communication systems (e.g., CDMA (code division multiple access)2000 system, WCDMA (wideband CDMA) system, etc.).

Embodiments of the present invention can be implemented using variousmeans. For instance, embodiments of the present invention can beimplemented using hardware, firmware, software and/or any combinationsthereof.

In case of the implementation by hardware, a method according to eachembodiment of the present invention can be implemented by at least oneof ASICs (application specific integrated circuits), DSPs (digitalsignal processors), DSPDs (digital signal processing devices), PLDs(programmable logic devices), FPGAs (field programmable gate arrays),processor, controller, microcontroller, microprocessor and the like.

In case of the implementation by firmware or software, a methodaccording to each embodiment of the present invention can be implementedby modules, procedures, and/or functions for performing theabove-explained functions or operations. Software code is saved in amemory unit 1380/1390 and is then drivable by a processor 1320/1330. Thememory unit may be provided within or outside the processor to exchangedata with the processor through the various well-known means.

While the present invention has been described and illustrated hereinwith reference to the preferred embodiments thereof, it will be apparentto those skilled in the art that various modifications and variationscan be made therein without departing from the spirit and scope of theinvention. Thus, it is intended that the present invention covers themodifications and variations of this invention that come within thescope of the appended claims and their equivalents. And, it isapparently understandable that an embodiment is configured by combiningclaims failing to have relation of explicit citation in the appendedclaims together or can be included as new claims by amendment afterfiling an application.

INDUSTRIAL APPLICABILITY

Accordingly, the present invention may be applicable to various wirelessaccess systems. And, 3GPP (3rd generation partnership project), 3GPP2and/or IEEE 802.xx (institute of electrical and electronic engineers802) system and the like are examples for the various wireless accesssystems. Embodiments of the present invention may be applicable to alltechnical fields having the various wireless access systems appliedthereto as well as the various wireless access systems.

1-16. (canceled)
 17. A method for receiving downlink ACK/NACKinformation in a wireless access system supporting a carrier aggregationscheme, the method performed by a user equipment (UE) and comprising:receiving a physical downlink control channel (PDCCH) including downlinkcontrol information (DCI) from a base station (BS) on a first componentcarrier (CC), wherein the DCI includes a carrier indicator field (CIF)indicating a second CC and scheduling information; transmitting uplinkdata on the second CC indicated by the CIF through a physical uplinkshared channel (PUSCH) based on the scheduling information to the BS;and receiving a downlink ACK/NACK information for the PUSCH from the BSon the first CC, wherein the first CC and the second CC are included ina plurality of CCs which are assigned to the UE.
 18. The method of claim17, wherein the downlink ACK/NACK information is transmitted throughphysical HARQ indicator channel (PHICH).
 19. The method of claim 17,wherein a location of the CIF is fixed in a front part of a payload ofthe DCI and wherein the CIF is fixed in size to a number of bits neededto identify each of a plurality of component carriers in the carrieraggregation scheme.
 20. The method of claim 19, wherein the location ofthe CIF is fixed regardless of DCI format.
 21. The method of claim 19,wherein the size of the CIF is fixed at 3 bits.
 22. A user equipment(UE) for receiving downlink ACK/NACK information in a wireless accesssystem supporting a carrier aggregation scheme, the UE comprising: areceiver; a transmitter; and a processor functionally connected with thereceiver and the transmitter, wherein the processor controls: thereceiver to receiver a physical downlink control channel (PDCCH)including downlink control information (DCI) from a base station (BS) ona first component carrier (CC), wherein the DCI includes a carrierindicator field (CIF) indicating a second CC and scheduling information;the transmitter to transmit uplink data on the second CC indicated bythe CIF through a physical uplink shared channel (PUSCH) based on thescheduling information to the BS; and the receiver to receiver adownlink ACK/NACK information for the PUSCH from the BS on the first CC,wherein the first CC and the second CC are included in a plurality ofCCs which are assigned to the UE.
 23. The user equipment of claim 22,wherein the downlink ACK/NACK information is transmitted throughphysical HARQ indicator channel (PHICH).
 24. The user equipment of claim22, wherein a location of the CIF is fixed in a front part of a payloadof the DCI and wherein the CIF is fixed in size to a number of bitsneeded to identify each of a plurality of component carriers in thecarrier aggregation scheme.
 25. The user equipment of claim 24, whereinthe location of the CIF is fixed regardless of DCI format.
 26. The userequipment of claim 24, wherein the size of the CIF is fixed at 3 bits.